Error "Card 85 does not exist" when joining two questions

I have two Questions in Metabase that retrieve data from different databases. I am trying to create a 3rd question that joins these two Questions. However, I get the error "Card 85 does not exist.".

Can you please let me know how to troubleshoot this error? Do you know if what I am trying to do should be possible?

I am running the latest version of Metabase Open Source 0.49.3 and I have cache disabled.

Thank you,